Fine weather and Indian summer not that unusual

Although the fine weather over recent days might seem anomalous, or even freakish, it is in fact common enough for a spell of…

Although the fine weather over recent days might seem anomalous, or even freakish, it is in fact common enough for a spell of quiet, settled, anticyclonic conditions to occur around this time of year, writes Brendan McWilliams.

Indeed, sooner or later almost every autumn, the normal procession of eastward-moving depressions is interrupted for a time, and a short-lived cell of high pressure develops over western and northern Europe.

It is a sort of encore that even the most mediocre summer cannot quite resist, a welcome respite that occurs with sufficient regularity for it to have become a feature of the folklore in many countries.

In olden times, it was common to link the supposed occurrence of such a spell to the nearest date of consequence on the church calendar. If, for example, the anticyclone happened to establish itself in very early autumn, it became "St Michael's Summer", linked to his feast day on September 29th.

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If, on the other hand, the fine spell occurred in mid-October, it became "St Luke's Summer", a turn of phrase which is associated with St Luke's feast day on October 18th.

"All Hallow's Summer" - or "All Saints Rest" as they call it up in Scandinavia - was a fine spell beginning sometime around All Saints Day on November 1st, and which is precisely what we have experienced this year. Should this fine weather last a bit longer it would merge into "St Martin's Summer", which was the name given to a fine spell starting around the feast day of St Martin of Tours on November 11th.

In this case, the story went that on a bleak morning in early November, the affluent Martin gave half his cloak to a poor man shivering with cold.

Pleased with Martin's conduct, the good Lord set the sun shining warmly until the saint could provide himself with another garment, and it was furthermore ordained that in commemoration of the kindly deed, the same spell of fine weather would occur forever more in the days leading up to mid-November. Clearly, the Lord is a bit forgetful sometimes, or perhaps mistakes the date.

Perhaps the best-known expression for autumnal warmth and sun, albeit not related to any specific date, is that of "Indian Summer".

The term relates to a brief spell of warm and pleasant weather like we have had in recent days that was regularly anticipated every year by the Native Americans, and used by them to prepare for the harsh winter on the Great Plains.

Although most of the country has seemed relatively balmy during recent days, the average temperature of the first week of November is running slightly below normal.

This is because despite the sunny days, most nights have been cold and frosty, dragging down the average.

In October, by contrast, southerly or southwesterly winds prevailed and brought frequent spells of heavy rain; but the nightly blanket of cloud resulted in an exceptionally mild month, with mean air temperatures close to two degrees higher than the norm.

Indeed it was the warmest October since 1969 along the western coast.

This followed the warmest September on record, which came at the end of a very warm summer.

In Ireland, summer 2006 was the warmest since those halcyon days of 1995 and in the extreme north, it was the warmest since temperature records began at Malin Head in 1885.

Across the channel, May to September this year was one of warmth unprecedented in the 350 years for which records are available, and in July, produced the warmest month recorded to date in England.

On the other side of the Atlantic, the average temperature from January to September 2006 in the US was the warmest yet recorded for this nine-month period.

So although there is nothing particularly unusual about the All Hallow's Summer we have enjoyed in recent days,the overall pattern of our weather is one where national and global temperatures are consistently above the levels of a quarter of a century ago; temperature records are being broken regularly, and successive months and years are warmer than their corresponding predecessors with increasing frequency.